Right now the world is working on various techniques to perform this task. Optimization comes later. Various different methods and mechanisms are being tried in orbit on test objects taken to space, but this one is a test with real space junk that has been there for a decade, so far. The vulnerability of the mission to the possibility of a change in shape of the target due to this collision shows how early we are in this technology. This is less of a debris removal mission than it is a proof of concept mission. Until the concept is shown to be feasible, then they can work on optimizing the missions so that each is less expensive. With refueling, a vehicle may be able to remove several pieces of junk.

Other concepts have been tried before, some of them did not work out as well as hoped. A “zap” may work for small junk, but the size that it might work on are too small to track (generally, less than 10 cm, or 4 inches, is difficult to track, and as the size gets smaller, tracking gets harder). Physically touching the target has a desirable amount of reliability. If you look up patents on this subject (and I have), you will find one idea of using an explosive high in the atmosphere to “throw” a mass of air high enough to increase the drag during one pass of a target object, but this presents other problems, such as additional satellites, perhaps living satellites, may also pass through that mass before the mass falls back in place, and control of the final reentry is difficult, so directing reentry of large debris into the Pacific may not happen.

Among the multitude of problems to overcome is that many objects are alone in their orbital planes. Unlike the movie Gravity, it is very difficult (propellant-expensive) to change orbital planes by much. To use a single spacecraft to eliminate multiple pieces of debris would be most successful if multiple items were in the same orbital plane. There are several cases of this, such as the pieces that seem to have been broken off this ring. Refueling may help, especially if the vehicle focuses on nearby orbital planes.

The movie may have been good at emphasizing the Kessler Effect, but it lost a lot of sense of reality in doing it.

Relative to the speed that orbital objects are traveling, it does not take much to get them to drop out of orbit. A speed change of around 250 meters per second (1/4 kilometers per second) is all that is needed to deorbit from low Earth orbit (orbital speed: around 8 kilometers per second). If you are not in a hurry to get rid of the piece of junk and it is small enough that you don’t care where it reenters, perhaps because it will all burn up, then you don’t have to slow it down quite as much, but it may spend a few years before it reenters.

Another problem is that the target junk may not be the same shape and size as the previous junk or the next junk to be targeted. Look at the worry that ESA has over a couple of pieces having been knocked off a 100 kilogram conical-shaped adapter, thinking it may complicate grabbing onto it.. How do you grab a satellite without knocking off small pieces, such as solar arrays or antennas? If you knock off pieces, haven’t you made the problem worse, not better? Remote control may be better than autonomous for the amount of care that is needed, but then you need humans in the loop, and that also gets expensive.

Space debris removal is a new industry, and it is working on the solutions that are needed and that will work. Efficiency and cost control are farther in the future.

Tom Billings,
It isn’t just satellites, it is other objects, too, such as upper stages and parts that have come off. Different sized satellites would have to have different standard interfaces, and we already have a standard interface ring with many of the geostationary satellites.

The problem comes in “dual-use” of a general technology. People don’t want to make it easy for hostile powers to de-orbit their satellites. Who is hostile? For now, it is anyone who wants a satellite to stop talking to people on Earth about what it’s heard, or what it sees, on Earth, or in Space. That is why people are promoting standardized interfaces for use by people who they believe will not become hostile. It still has the problem that it divides our species into “those we want talking to us”, and “those who don’t want their people talking to us”.

This *may* be resolved with something as large and cheap as a Starship version, running around Low Earth Orbit, picking up hundreds or thousands of debris pieces by simply engulfing them in a large cargo maw, using ion engines to slowly collect many thousands of debris pieces we think belong to our responsibility. Each nation sending up satellites is responsible for its own debris, and we cannot, under the OST, disturb their stuff.